The utility of computer systems can be enhanced by providing better user interfaces. User interfaces for computers systems have evolved significantly since the personal computer (PC) first became widely available. Early PCs used rather primitive user input devices, such as the serial mouse. However, the vast improvement in microprocessors, available memory, and programming functionality have all contributed to the advancement of user interface design and the development of user friendly graphic operating systems and hardware. One particular area of advancement in user interface technology pertains to the detection of an object near a user interface, which is sometimes referred to as proximity detection. Generally, as applied to user interfaces, proximity detection is thus concerned with the detection of objects, including inanimate objects and/or a user's hand or finger, for example, when in proximity of a user interface or surface.
There are several detection technologies that may be used for proximity detection in connection with a user interface, including capacitance-based systems, and various optical-based detection systems. The following discussion focuses on the use of optical-based proximity detection. Optical-based proximity detection techniques have been developed that provide for illuminating an entire user interface surface with light and employ a digital video camera to recognize objects that are either in contact or proximate to a graphic display surface, based upon the light reflected from the objects. Such systems require sufficient illumination of the user interface surface by the system to overcome ambient illumination in order to differentiate objects within the view field of the digital camera. Methods to reduce the undesired effects of ambient light on detecting objects in such systems include increasing the number of illumination sources, increasing the power of the illumination sources, polarizing the illumination light emitted by the light sources used to detect objects, filters for wavelength discrimination, and various modulation techniques. Each of these techniques have drawbacks in achieving the desired even illumination of the view field.
Another recent development with regard to user interfaces for computer systems includes the advent of interactive displays. An interactive display presents graphic images to a user on a flat surface, such as the top of a table. A PC is coupled to the interactive display to provide a rich user interactive experience that offers more sophisticated command and interface features, and a far more natural interactive experience in providing input to the system. An initial embodiment of the interactive display employs proximity-detection for responding to the user interaction with the display surface, but has experienced some of the problems noted above that are common to other optical-based object proximity detection systems. Therefore, it has become more important to provide a more robust optical object proximity detection scheme that is less effected by ambient light.